The present invention relates to production of pipes and in particular to pipe-welding mills for production of coiled pipes by argon-arc welding.
The pipe-welding mill forming the subject of the present invention may be used to advantage in production of welded thin-walled pipes wherein the ratio of an outside diameter to wall thickness is about 60, the welding being accomplished at a speed of 15 m/min approximately.
Known in the art is a pipe-welding mill for production of coiled pipes, comprising a strip preparation section including a coil magazine, an unwinder, a butt-welding device, shaping and sizing stands, a welding stand, a cutting arrangement, a guide system, differential switches, feeding machines, and winders (cf. "Equipment for Coiling Water and Gas Pipes Using a Continuous Furnace Welding Mill", UDC 621.774.21, Informtyazhmash SRI, 1-72-9, in Russian).
In the aforesaid mill the pipes may be coiled continuously by installing guide systems, differential switches for dividing the pipe flow between two winders, and feeding machines after the cutting arrangement, a feature substantially complicating its construction and entailing an intricate maintenance procedure.
Also used in pipe production in the USSR is a mill comprising a coil preparation section with two double-seat rotatable unwinders mounted on a platform disposed in a manner allowing its displacement in a direction perpendicular to the mill axis and with magazines containing coiled strip and mounted in the seats of the unwinders, a machine for coupling strip ends, shaping, welding, and drawing stands, a cutting arrangement, a guide for directing the pipe into bending rollers, feeding rollers, a coiling arrangement with two bending rollers having fixed axes and one bending roller having a movable axis, and also with a mechanism controlling the latter roller, a receiving arrangement with parallel rollers having a common drive with the bending rollers, the rollers of the receiving arrangement being rigidly attached to the output shafts of the drive, axes thereof being parallel to the axes of the bending rollers. Installed between the receiving rollers is a remover including a drive and grips.
However, the foregoing mill has been generally unsatisfactory due to intricate construction and a comparatively low operational reliability, a disadvantage associated with the fact that the cutting arrangement located ahead of the bending rollers of the coiling arrangement calls for the utilization of additional mechanisms such as a guide, feeding rollers, and a mechanism controlling the bending roller, said mechanisms being required to direct the forward end of the subsequent pipe into the bending rollers, to control the bending roller at the instant the forward end of the subsequent pipe enters the bending area, and to provide a sufficient gap between the forward end of the subsequent pipe and the tail end of the preceding pipe which is coiled, said gap being left to remove the coiled pipe. Furthermore, the known mill has been open to the objection that the rigidly fixed receiving rollers employ devices for removing the coiled pipe, said devices having an individual drive and a chain drive with grips that may deform the pipe as they return to the original position and also during entry between the turns of the preceding and subsequent coils.